1. Field of the Invention
This invention relates in certain embodiments to high density, nontoxic articles such as shots used as projectiles in shotgun shells and the like.
2. Description of the Related Art
Lead has traditionally been used as a material for shot pellets for hunting, especially hunting for birds, because of its high density and low melting point that lend itself to ease of manufacture and highly predictable ballistic characteristics. The majority of these pellets fall to the ground without hitting the target. Some of them settle on the bottom of the wetlands and lakes. Over time the spent lead pellets accumulate to a point that some waterfowl have shown signs of lead poisoning because they ingested lead pellets while in search of food and also the grit to assist in digestion of the food. This has led to the ban of lead shot pellets for waterfowl hunting in the U.S., Canada, and other countries.
Because of market demand, considerable effort has been devoted to searching for a viable lead substitute that can be economically produced and at the same time possesses the predictable ballistic characteristics of the lead shot pellet, such as uniform pattern density with a wide variety of shotgun chokes and barrel lengths, and uniform muzzle velocities with various smokeless powders. There are no comparable metals that possess all of the desired characteristics. Those metals that are somewhat close to lead in density are not satisfactory substitutes as a result of other drawbacks, such as high cost, radioactivity, high melting point, or other properties.
Various approaches have been proposed to formulate a mixture of metals and in some cases using polymers. Additionally, various methods have been attempted to process these mixtures for the final product. Despite these prior efforts, the products made according to these materials and processes have some shortcomings as discussed below.
Steel was selected as the most practical substitute, based on methods of production, cost, ballistics, and its nontoxic nature. However, steel shot pellets have a density of about 7.5 to about 8.0 g/cm3 as compared to lead alloy shot pellets which have a density of about 10 to about 11 g/cm3. Density differences between shots of the same gauge will perform differently in the trajectory and firearm recoil when powered by the same charge. Additionally, steel shot pellets do not deform, and have a definite tendency toward center density regardless of choke. Especially for the large size steel shots, they do not pattern perfectly from tightly choked barrels because such charges do not swage down well to flow smoothly through the choke. The wedging and bridging were believed to be the reasons in an overly choked condition. To compensate for the density difference, hunters have been using two or three larger gauge shot pellets in the shotshell load. Unfortunately, the larger shot pellet size reduces the total number of shot pellets that can be loaded in the predefined shotshell case; this in turn deteriorates the pattern density. Because of the hardness of the steel shot pellet, it is required to have a thicker and harder plastic to protect the bore from the ravages of the steel shot pellets. This requirement further reduces the case volume available for the shot pellets. In order to increase the case volume to accommodate more steel shot pellets, the wad has been redesigned to eliminate the collapsible leg section.
The larger diameter steel shot pellets suffer more disadvantages. The larger steel shot pellet will lose velocity quicker than the smaller high density shots. Also, the steel shot pellet will not penetrate as well because of its larger frontal section. This, coupled with low density, loss of velocity due to drag force, and the inferior pattern density previously mentioned, have resulted in an increased number of crippling shots. Hunters have been known to reduce the range over which he or she will try to take game by as much as 25%. Also, because the steel shot pellets lose momentum over the flight range, they require a lengthened lead. Some manufacturers have employed special powder to drive up the muzzle velocity, but these powders also increase the barrel pressure which causes safety concerns. All of these issues cause a great deal of confusion and frustration to the hunting community.
Nontoxic shot products currently in the market are either too hard or too soft, too frangible or too rigid, or too abrasive. Products that are too hard or too rigid damage the gun barrel and have a strong tendency to ricochet when hitting a hard surface. Products that are too soft tend to leave some rub off particles in the gun barrel and deform too much at firing and in flight, which causes deterioration in the shot pattern and final impact energy and energy transfer. It is also harder for a soft shot to penetrate the animal to make a clean kill. Products that are too frangible tend to crack during set back (firing), and in flight; this will cause drag in flight and cause the shot to lose momentum. It also tends to cause the shot to disintegrate upon impact, thus impeding penetration and causing the energy to not transfer onto the animal.
The majority of the prior nontoxic shots have not proved to be commercially viable primarily due to high equipment cost, high process operating cost, inferior density and hardness characteristics compared to lead and lead alloy.